Test system for analyzing body fluids

ABSTRACT

The invention relates to a test system for analyzing body fluids of the type comprising a test element tape carrying a plurality of test elements, a tape deflector for the test element tape for the selective application of body fluid, and a light source as well as a detector for optically analyzing test elements to which body fluid has been applied. The tape deflector has a rotatable optical element which acts as a deflection roller during transport of the test element tape. The optical element is positioned in the optical path between the light source and the detector.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/468,049 now U.S. Pat. No. 7,708,948 filed Aug. 29, 2006,which claims priority to EP 05 018 973, filed Sep. 1, 2005.

BACKGROUND

The present invention relates to a test system for analyzing bodyfluids, in particular blood, of the type comprising a test element tapecarrying a plurality of test elements that is preferably wound in a tapecassette, a tape deflector for the test element tape for the directedapplication of body fluid, and a light source as well as a detector tooptically analyze test elements to which body fluid has been applied.

Portable devices operating as minilaboratories, which can also be usedby laymen to carry out the required steps in a simple and rapid mannerare known for self-monitoring blood glucose by diabetics. In order toreplace conventional test strips, it is proposed in WO 2004/047642 thatinstead of individual test strips, a wound test tape should be used onwhich a plurality of test fields provided with a suitable test chemistryare arranged consecutively. The body fluid is applied to a test fieldthat is moved into an active position by advancing the tape over a tipand analyzed. Details on blood collection as well as on the known testmedia and detection systems especially for blood glucose are disclosedin this document to which reference is herewith made and the contents ofwhich are incorporated by reference into this application. This documentalso shows that a transparent tip can be used to directly couple theinstrument optics. Constraints that have to be observed in this case arethat the total height of the deflector tip and its opening angle shouldbe as small as possible but it should still be possible to opticallyanalyze the test field for example on the basis of a reflectancemeasurement or a fluorescence measurement.

SUMMARY OF THE INVENTION

The present invention addresses the above-noted disadvantages andprovides an improved and simplified system of the type mentioned above,and in particular, also reduces strain on the test tape in order toachieve a reliable measurement process in a compact instrument.

Exemplary embodiments of the present invention provide a deflector forthe test tape which is advantageous for tape transport as well as foroptical analysis. In exemplary embodiments, the tape deflector has arotatable optical element positioned in or along the optical pathbetween the light source and the detector. The optical element rotatesto transport the test tape. The optical element, which rotates duringtape transport, considerably reduces frictional losses in the tapedeflection, thus considerably reducing the risk of tape deformation orof a tear in the tape. This also allows the use of thinner carriertapes, which in turn, allows a greater quantity of tests to be providedwithin a given cassette volume. Moreover, the tape can be transportedwith less motor output and at the same time with less power consumption.The transparent optical element also creates a simple optical access tothe test element without the test element having to be transportedfurther to a distant measuring position.

The light permeable optical element preferably has a deflector surfacethat rests against the test element tape and can be rotated in thedirection of tape transport to ensure a direct optical coupling in themeasuring position and a rotation of the deflector as the tape advances.

Another advantageous embodiment provides that the optical elementconsists of a lens which focuses the light of the light source onto therespective test element to be analyzed on the test element tape. Thisallows imaging effects to be utilized for a miniaturization of themeasuring field.

Another constructional improvement is achieved by designing the opticalelement as a cylindrical lens which is mounted so that it can rotatefreely about its longitudinal axis and guides the test element tape onits outer surface.

For tape transport, it is favorable when the optical element has acircular, elliptical or polygonal rotationally symmetric cross-section.

The optical element can be rotatably mounted in a sleeve bearing, apivot bearing or conical bearing to provide a simple bearing withsufficiently low friction.

Another advantageous embodiment of the optical coupling provides thatthe optical element in combination with a lens located downstream of thelight source and/or upstream of the detector forms the imaging optics.

In order to screen the detector from ambient light, it is advantageouswhen a diaphragm is located in the area of an intermediate image betweenthe test element tape and the detector.

According to a further exemplary embodiment, the detector is arrangedoutside of the area of incidence or of the optical axis of the lightspecularly (directly) reflected from the test element or of the lightbeam of the light source. In this manner it is possible to differentiatepurely geometrically between the diffusely (in all directions) reflectedlight which provides the information on the analyte from the reagentlayer of the test field, whereas the specular reflection does not reachthe entry cross-section of the detector, at least not to a significantextent.

Such a geometric separation can be achieved by aligning the light sourceat an angle of incidence to the test element tape and aligning thedetector at a larger detection angle in comparison thereto in a commonplane on one side of the axis of incidence.

Another advantageous arrangement provides that the light source and thedetector are arranged in a common half-space at a lateral distance froma boundary plane spanning the center line of the test element tape inthe region of the tape deflector. The light that is reflected normallyis essentially radiated into the other half-space without reaching thedetector.

From a constructional point of view it is particularly advantageous whenthe light receiver and the detector are arranged on a support in aninstrument which receives the tape cassette and are aligned with thetape deflector by means of an optical deflection means and in particularby a mirror integrated in the tape cassette.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present invention and the manner ofobtaining them will become more apparent and the invention itself willbe better understood by reference to the following description of theembodiments of the invention taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of a blood sugar measuring instrument witha tape deflector for use of a test element tape;

FIG. 2 is a simplified cross-sectional view illustrating the tapedeflector provided as a rotatable cylindrical lens in conjunction with areflectometric measuring device;

FIG. 3 shows a longitudinal section through the arrangement of FIG. 2;

FIG. 4 shows another embodiment of an optical deflection roller in aview corresponding to FIG. 3;

FIG. 5 shows a polygonal deflection roller in profile;

FIG. 6 is a perspective view of a cassette part containing thedeflection roller for the test element tape;

FIG. 7 is a sectional perspective view showing a measuring arrangementof the blood sugar measuring instrument; and

FIG. 8 shows a partial sectional side-view of the arrangement of FIG. 7.

Corresponding reference characters indicate corresponding partsthroughout the several views.

DETAILED DESCRIPTION

The embodiments of the present invention described below are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather, the embodimentsare chosen and described so that others skilled in the art mayappreciate and understand the principles and practices of the presentinvention.

FIG. 1 shows a test system for body fluids and in particular a bloodsugar measuring instrument 10 in the form of a portable hand-heldinstrument. It includes an instrument housing 12 with a display 14 inwhich a tape cassette 16 can be inserted as a consumable part. Thecassette contains a test element tape 18 which is expediently providedwith test elements or test elements 20 spaced apart on sections thereof.Body fluid (blood) can be applied to the test elements 20 in order toquantitatively detect an analyte (glucose) contained therein by means ofa reflectometric measurement.

The individual test elements 20 are moved successively into a receivingposition or testing position in the deflection area in which their frontfaces are accessible for a selected application of a small amount ofbody fluid by winding the test tape 18 forwards over a tape deflector 22that has a basic V-shaped form. The optical measurement takes place fromthe rear side of the tape through the tape deflector 22 wherein the testelement tape can have a transparent carrier foil or a tape cut-out inthe area of the test elements 20. After measurement, the used testelement 20 is wound onto a take-up spool of the tape cassette 16 duringwhich an unused test field on the adjoining section of tape is drawn offfrom a supply spool. In this manner the user can carry out a pluralityof tests in an automated measuring process without requiring complicatedhandling steps.

As shown in FIG. 2, the tape deflector 22 has a transparent rotatablelens element 24 positioned in the optical path 26 of the opticalmeasuring device 28. The outer wall 30 of the circularly cylindricallens element 24 composed of glass or transparent plastic forms adeflection surface which rotates with the test element tape 18 duringtape transport so that only slight frictional losses occur. At the sametime, the lens element 24 focuses the measuring light generated by thelight source 32 of the measuring device 28 onto the test element 20 thatis present at that time in the receiving position. In order to improvethe light yield, a converging lens can be arranged in front of it.

FIG. 3 shows a possible sleeve bearing of the cylindrical lens 24 in theform of front-facing pivot bearings 36 in the side walls 38 of thecassette 16. FIG. 3 also shows a possible arrangement of the lightsource 32 and detector 40 of the measuring device 28 for the detectionof the measuring light that is diffusely reflected from the test element20. For this purpose, the detector 40 is arranged outside of the opticalaxis of the light from the light source 32 that is specularly reflectedfrom the facing rearside of the test element 20. In the embodimentillustrated in FIG. 3, the light source 32 and the detector 40 arealigned in one plane which extends through the axis of rotation 42 ofthe cylindrical lens 24 and the zenithal line 44 of the tape deflectorwherein the detector 40 is arranged at a larger receiving angle βcompared to the beaming angle α of the light source 32.

FIG. 4 shows another alternative for the simple pivoting of thecylindrical lens 24. In this example front-facing conical bearings 46are provided for a low friction point contact. A low positioningtolerance is employed, especially perpendicular to the axis of rotation42, as well as low friction and ability to be manufactured economically.

As shown in FIG. 5, the lens or deflection roller 24 can also have apolygonal geometry instead of a circular cross-section. In theembodiment shown, the basic shape is that of a pentagon in order to thusachieve better defined transport paths for the tape transport. In thiscase, the side surfaces 48 are rounded or chamfered in order toadvantageously design the optical paths.

According to FIG. 6, the tape cassette 16 can have a cassette tip 50with V-shaped converging tape guide surfaces 52 where the cylindricallens 24 is positioned in the apex region. Form-locking structures (notshown) can be provided within the cassette tip 50 for exact alignmentwhen the measuring device 28 is attached where openings in the walls 54,56 allow the light source and detector to be engaged from below.

As shown in FIGS. 7 and 8, the light source 32—in the form of three LEDs58—and the detector 40 are arranged on an instrument mainboard 60,whereas the optical light path is determined by elements on thecassette. In detail, these elements are a deflecting mirror 62, aconverging lens 34 and the cylindrical lens 24 as a deflection rollerfor the test tape 18. The lens 34 arranged in front has a simple convexlens surface 64 facing the deflection roller and a double convex lenssurface 66 facing the measuring device 28 where a central diaphragm 68between the lens segments separates the light source 32 from thedetector 40.

Also in this case the geometric arrangement of the optical elementsensures that only light that is diffusely reflected from the rear side70 of the test element 20 is detected. For this purpose the light source32 and the detector 40 are arranged in the half-space below the planeextending through the centre line 74 of the test tape such that thespecularly reflected light is essentially radiated into the half-spaceabove it. Calculations made on this configuration show that theproportion of specularly reflected light detected in the detectorrelative to the total emitted light of the light source is less than0.001 ppm whereas the ratio of detected to emitted light is about 0.13%.Hence, this ensures that mainly only diffusely reflected light from thereagent layer of the test element 20 is detected.

In summary, it may be ascertained that the embodiments disclosed hereinconcern a test system for analyzing body fluids and in particular bloodcomprising a test element tape 18 carrying a plurality of test elements20, a tape deflector 22 for the test element tape for the selectiveapplication of body fluid and a light source 32 as well as a detector 40for optically analyzing test elements to which body fluid has beenapplied. The tape deflector 22 has a rotatable optical element 24 as adeflection roller to transport the test element tape 18 in the opticalpath between the light source 32 and detector 40.

While exemplary embodiments incorporating the principles of the presentinvention have been disclosed hereinabove, the present invention is notlimited to the disclosed embodiments. Instead, this application isintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

LIST OF REFERENCE NUMBERS

-   -   10 Blood sugar measuring instrument    -   12 Instrument housing    -   14 Display    -   16 Tape cassette    -   18 Test element tape    -   20 Test element    -   22 Tape deflector    -   24 Lens element    -   26 Optical path    -   28 Optical measuring device    -   30 Outer wall    -   32 Light source    -   34 Converging lens    -   36 Front-facing pivot bearing    -   38 Side wall    -   40 Detector    -   42 Axis of rotation    -   44 Zenithal line    -   46 Front-facing conical bearing    -   48 Side surface    -   50 Cassette tip    -   52 Tape guide surface    -   54 Opening in the wall    -   56 Opening in the wall    -   58 LED    -   60 Instrument mainboard    -   62 Deflecting mirror    -   64 Convex lens surface    -   66 Double convex lens surface    -   68 Central diaphragm    -   70 Rear side    -   74 Centre line

1. A method of using a test system having a test element tape foranalyzing body fluids, comprising: positioning an optical elementadjacent the test element tape; advancing a test element of the testelement tape to a testing position while rotating the optical element;projecting light through the optical element and onto the test element;and detecting light that is reflected from the test element and thatpasses through the optical element.
 2. The method of claim 1, furthercomprising the steps of: applying a body fluid sample to the testelement prior to the projecting step; and analyzing the detected lightfor presence or concentration of an analyte in the body fluid sample. 3.The method of claim 2, wherein the analyte is glucose.
 4. The method ofclaim 1, wherein the optical element is cylindrical.
 5. The method ofclaim 1, further comprising frictionally engaging the optical elementwith the test tape while advancing the test element.
 6. The method ofclaim 1, further comprising passing one of the projected and thedetected light through a second optical element.
 7. The method of claim1, wherein the step of positioning the optical element comprisespositioning the optical element adjacent and in contact with the testelement tape.
 8. The method of claim 1, wherein the step of projectinglight comprises using a light source to project light through theoptical element.
 9. The method of claim 1, wherein the test element isadvanced by the rotating of the optical element.
 10. A method of using atest system having a test element tape for analyzing body fluids,comprising: positioning an optical element adjacent and in contact withthe test element tape; advancing a test element of the test element tapeto a testing position while rotating the optical element; projectinglight through the optical element and onto the test element; anddetecting light that is reflected from the test element and that passesthrough the optical element.
 11. The method of claim 10, furthercomprising the steps of: applying a body fluid sample to the testelement prior to the projecting step; and analyzing the detected lightfor presence or concentration of an analyte in the body fluid sample.12. The method of claim 11, wherein the analyte is glucose.
 13. Themethod of claim 10, wherein the optical element is cylindrical.
 14. Themethod of claim 10, further comprising frictionally engaging the opticalelement with the test tape while advancing the test element.
 15. Themethod of claim 10, further comprising passing one of the projected andthe detected light through a second optical element.
 16. The method ofclaim 10, wherein the step of positioning the optical element comprisespositioning the optical element adjacent and in contact with a testelement.
 17. The method of claim 10, wherein the step of projectinglight comprises using a light source to project light through theoptical element.
 18. The method of claim 10, wherein the test element isadvanced by the rotating of the optical element.